Method of protecting cylinder liner transfer openings from casting material during injection die-casting of cylinders



3,149,383 YLINDER LINER TRANSFER OPENINGS FROM INJECTION DIE-CASTING OFCYLINDERS Filed Feb. 13. 1961 M GR mm E m G mm mm EA MC Sept. 22, 1964INVENTORS Mox Seyffer Leopold Ruess MWyW ATTORNEYS United States PatentMETHQD 0F PROTECTING CYLINDER LINER TRANSFER GPENINGS FROM CASTING MATE-REAL DURING INJECTION DIE-CASTING OF CYLINDERS Max Seyfier and LeopoldRuess, Munich, Germany,

assiguors to Rockwell G.rn.h.H., Pinneherg, near Hamburg, Germany, acorporation of Germany Filed Feb. 13, 1961, Ser. No. 103,181 Claimspriority, application Germany Feb. 26, 1960 2 Claims. (Cl. 22203) Thisinvention relates to a method of protecting cylinder liner transferports from the casting material used in the die-casting method offorming cylinders around a preformed liner, the cylinders being used forinternal combustion engines, particularly two-stroke engines.

There are known methods of injection die-casting a cylinder over apreformed cylinder liner, for use in twostroke internal combustionengines, in which transfer passages lead from the base of the cylinderup to transfer ports in the wall of the cylinder liner. In at least onepreviously known die-casting method the cores used to form the transferpassages in the cylinder casting have upper ends shaped to exactly coverpre-formed transfer ports in the cylinder liner, the arrangement beingintended to prevent entrance of the casting material into and around theedges of the cylinder liner transfer ports. In following that knownmethod, the cores used to form the transfer passages must comply exactlywith the shape of the cylinder liner transfer ports, thus dictatingmanufacture of the cylinder liner to very close tolerances, particularlywithin the region of the transfer ports. It has been found that evenwhen the cylinder liner manufacture and the core formation are held toclose tolerances, entrance of casting material past the core and intothe transfer ports cannot be completely prevented due to the extremelyhigh pressure, approximately 4500 psi, used during the injection castingprocess. Under these high pressures the casting material is capable ofpenetrating the most minute gaps and openings. Other known methods usemultiple port movable cores to shift into the liner openings, but evenso, the extremely close tolerances between cores and liner make the costexcessive.

Accordingly, the primary object of the present invention resides inimproving the process of injection die-casting of cylinders aroundcylinder liners by the novel procedure of prefilling the cylinder linertransfer ports or other openings with a filling material substantiallyinert to the material of the liner, resistant to pressure of theinjection process and easily removable upon completion of the castingoperation.

Further novel features and other objects of this invention will becomeapparent from the following detailed description, discussion and theappended claims taken in conjunction with the accompanying drawings,showing a preferred manner of carrying out this invention:

FIGURE 1 is a vertical section through the die and cylinder linerassembly illustrating the manner in which the present invention isutilized in an injection die-casting process; and

FIGURE 2 is a section view taken on lines 22 of FIGURE 1 to illustratethe relationship of the transfer passages, their molding cores and thefilled transfer openings of the cylinder liner.

To illustrate the improved die-casting process, representativecomponents used in injection die-casting of a two-stroke cycle internalcombustion engine cylinder around a ported liner are shown in FIGURES 1and 2. The drawings illustrate that stage of the process where injectiondie-casting has been completed and the die-cast cylinder and liner arestill within the mold forms.

3,149,383 Patented Sept. 22, 1964 The casting mold is made in threeparts: a lower part 10 which includes the interior core formations, andthe two upper parts 12 and 13 forming a split exterior casting form. Themold can be firmly secured by clamps or other normal means (not shown)to withstand the very high injection casting pressures of approximately4500 pounds per square inch.

Before assembling the mold to receive casting material, a cylinder liner14 having transfer ports 16 is slipped over the vertical core of thelower mold part 10. The liner 14, if desired, can itself be a pre-castcomponent. Included on lower mold part 16 are transfer passage cores 18which are disposed vertically up and adjacent the exterior side ofcylinder liner 14, fitting over the cylinder liner transfer ports 16.Transfer ports 16 in the cylinder liner 14 have been completelyprefilled with a special material 26 prior to the cylinder liner 14being slipped over the core of lower part 10. The exterior die parts 12and 13 are then placed over the assembled lower part It) and cylinderliner 14 after which injection die-casting of cylinder material isaccomplished to form cylinder 22 on and around the liner 14.

Transfer passage core parts 18 together with the cylinder liner transferport 16 result in inlet and outlet transfer channels through thecylinder 22 to the interior of the liner 14. After completion of theinjection molding operation the exterior mold parts 12 and 13 areseparated, enabling the finished unit of a cylinder .22 with itsinternal liner 14 to be drawn off the lower mold part 10: after whichthe transfer port filling material 26 is easily knocked out of the linerports 15. The presence of the port filling material 29 assures that nodie-casting fiash material or excess injection material is present atthe edges of and/ or within the cylinder liner transfer ports 16.

The importance of this invention resides in the fact that such flashesand projections of casting material which previously often resulted atthe joinder of the. inlet and outlet transfer passages and the cylinderliner transfer ports are now eliminated. Any such projections in thepath of fluid flow constitute serious interference with desired properflow characteristics through the transfer passage and into the cylinderliner and from the cylinder liner out through the other transferpassage. Interference with proper fiow effects the operatingcharacteristics efficiency of the internal combustion engine. Usingpreviously known methods of casting, it was very difficult, if notpractically impossible, to avoid such unwanted projections around theedges of the cylinder liner transfer openings.

It is realized that the objectionable projections and flashes at theedges of the transfer openings in the cylinder liner can be removed byadditional work steps, such as grinding, or they could be avoided byutilizing a rather complex mold which would include additional coreparts to fill the transfer port in the cylinder liner. However, there isconsiderable complexity when such additional core parts are used becausethey must be capable of being drawn into the interior of the verticalcore inside the cylinder liner. Besides being expensive and complicated,such a production method requires very close tolerances of the mold,mold components and, more particularly, a close working tolerancebetween mold core and shape of the transfer ports of the liner in orderto enable precise engagement of the movable cores which must shift intoand exactly fill the liner port openings. In order to assure success ofsuch a process, there are additional aspects which must be consideredand which increase the unfeasible, economic factors which make suchpreviously known process, unacceptable. One such factor is that theopenings in the liner, when die cores must move into the openings,cannot be formed in their final shape during the step of casting theliner but, because of requisite tolerances, must be subjected to furthermechanical treatment, such as grinding, to assure a close proper fit ofthe movable core in the port.

Exact grinding and peripheral shape of the transfer ports is in fact notreally necessary to assure proper functioning of the engine. Hence, inaccord with applicants invention, liners having transfer ports may beproduced by inexpensive methods, the tolerances of the port shapes beingdictated only by the necessary functioning in the engines for which theyare made, in other words, the transfer ports need no longer be formed toclose tolerances previously required not by the engine operation but bythe necessary close fit with extraneous mold parts used for injectioncasting of the cylinder around the liner.

Transfer ports with inclinations and intersections can be produced withno problems according to this method.

With the present method the cylinder liners can be made by an injectioncasting process and the cast surface can remain untreated insofar as thetransfer ports are concerned. Introduction of casting material into andaround the edges of the transfer openings during injection casting iseffectively completely avoided by the placing of an insert of expendablefilling material to completely fill the liner transfer ports prior tothe injection casting of material into the mold.

The three-part injection mold for die-casting the cylinder around theliner, in accord with the present invention, may be developed in thesimplest manner; it does not require pre-made movable internal coreparts for the liner transfer ports, nor does it require transfer passagecores which must exactly cover the transfer passages.

Referring again to the drawings, the filling material 20 which is placedin the cylinder liner transfer ports 16 should be some material inertrelative to the metal cylinder and liner, i.e., a material which willnot alloy with the casting or liner material and it must also be capableof withstanding high pressures while still retaining its shape. It maybe gypsum or some ceramic material or the like which can be utilized ina plastic condition and molded into shape within the ports 16.

It is also envisaged to use a filling body correspondingly preformed,for example, consisting of the prementioned materials or the like whichcan be inserted in the manner of a preformed plug into the transferports and readily removed after the injection casting process iscompleted. Material of the aforenoted constituency will neither alloywith the cylinder liner nor with the casting material used to make thecylinder around the liner.

The filling material can be readily and easily removed by lighttapes orblows upon completion of the injection casting of the cylinder andliner.

In accord with the aforedescribed invention, there is provided aninexpensive process for die-casting a cylinder on a cylinder liner, thecombination including transfer passages and transfer ports, therelationship between the passages and ports being such to provide theoptimum cross-sectional area with regard to the flow of combustion fluidenabling proper flow characteristics in the fin-, ished engine with thesmallest possible flow resistance to cause undesired and troublesomewhirls and non-turbulent dead spots. Transfer ports with inclinationsand sharp edge intersections can easily be produced according to thismethod.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

l. A method of die-casting a cylinder around a cylinder liner, the linerhaving at least one opening through the wall thereof and wherein thecast cylinder will include at least one passageway leading to theopening in the liner, the steps comprising: positioning a tubular metalliner having an opening in the wall thereof snugly upon a core portionof a die mold form with a surface of the core portion providingcomplementary surface contour continuity with the inner surface of theliner, engaging the inner peripheral edge of the liner opening andextending across the liner opening; completely filling the opening insaid cylinder liner with a plug of material which is pressure resistantand will not alloy with the material of the liner or the castingmaterial, the plug being in intimate engagement with the edges of theopening and having substantially the same thickness and contour of theliner; disposing the liner so a transfer passage core portion of themold form is positioned along the exterior side of said liner snuglyoverlying and engaging said filling material in said liner opening andterminates adjacent at least a part of the periphery of the opening;disposing an exterior die mold surrounding said liner and core portions;and die-casting a cylinder surrounding said liner by means of a highpressure injection casting process.

2. A method of die-casting a cast metallic structure surrounding ametallic insert, the metallic insert having at least one opening througha part thereof and wherein the die-cast additional structure willinclude at least one passageway leading to the opening in the insert,the steps comprising: positioning the metallic insert with at least itspart having the opening therethrough, disposed snugly against a rigidportion of a die-mold form so that the rigid portion of the die-moldform provides complementary surface continuity with the surface of themetallic insert around one end of the opening, engages the peripheraledge of the one end of the opening and extends across and therebyprovides a rigid backing surface over one end of said opening;completely filling the opening in the metallic insert with a plug ofmaterial which is pressure resistant and will not alloy with thematerial of the liner or with the casting material, the material plugbeing in intimate engagement with the edges of the opening and havingsubstantially the same thickness and contour continuity of the metallicinsert adjacent its opening; the positioning of the insert resulting ina passage core portion of the die-mold form being disposed adjacent theother end of the insert opening with a terminal portion of the passagecore snugly overlying and engaging the entire end surface of saidfilling material in the metallic insert opening; disposing an exteriordie-mold surrounding said metallic insert and mold form portions; anddie-casting I additional structure surrounding said metallic insert bymeans of a high pressure injection casting process.

References Cited in the file of this patent UNITED STATES PATENTS

1. A METHOD OF DIE-CASTING A CYLINDER AROUND A CYLINDER LINER, THE LINERHAVING AT LEAST ONE OPENING THROUGH THE WALL THEREOF AND WHEREIN THECAST CYLINDER WILL INCLUDE AT LEAST ONE PASSAGEWAY LEADING TO THEOPENING IN THE LINER, THE STEPS COMPRISING: POSITIONING A TUBULAR METALLINER HAVING AN OPENING IN THE WALL THEREOF SNUGLY UPON A CORE PORTIONOF A DIE MOLD FORM WITH A SURFACE OF THE CORE PORTION PROVIDINGCOMPLEMENTARY SURFACE CONTOUR CONTINUITY WITH THE INNER SURFACE OF THELINER, ENGAGING THE INNER PERIPHERAL EDGE OF THE LINER OPENING ANDEXTENDING ACROSS THE LINER OPENING; COMPLETELY FILLING THE OPENING INSAID CYLINDER LINER WITH A PLUG OF MATERIAL WHICH IS PRESSURE RESISTANTAND WILL NOT ALLOY WITH THE MATERIAL OF THE LINER OR THE CASTINGMATERIAL, THE PLUG BEING IN INTIMATE ENGAGEMENT WITH THE EDGES OF THEOPENING AND HAVING SUBSTANTIALLY THE SAME THICKNESS AND CONTOUR OF THELINER; DISPOSING THE LINER SO A TRANSFER PASSAGE CORE PORTION OF THEMOLD FORM IS POSITIONED ALONG THE EXTERIOR SIDE OF SAID LINER SNUGLYOVERLYING AND ENGAGING SAID FILLING MATERIAL IN SAID LINER OPENING ANDTERMINATES ADJACENT AT LEAST A PART OF THE PERIPHERY OF THE OPENING;DISPOSING AN EXTERIOR DIE MOLD SURROUNDING SAID LINER AND CORE PORTIONS;AND DIE-CASTING A CYLINDER SURROUNDING SAID LINER BY MEANS OF A HIGHPRESSURE INJECTION CASTING PROCESS.